This invention relates generally to safety lines and more particularly to a new and improved non-conductive safety line that may be used in the electrical industry as a simple rope-like link having strength and high dielectrical quantities that remain stable even when moist or wet.
While working on or around high-voltage equipment, rigid tools having appropriate insulation or flexible non-insulated or poorly insulated lines ae used to facilitate work on the energized equipment. Among these flexible lines or straps are what is known as safety lines which are utilized for persons working aloft. Safety lines are usually fastened around the worker's waist with the other end attached to some sturdy member in order to arrest a fall should the worker fall.
Whenever a power line is pulled, held, tied off or handled in any manner by the worker, an insulated device of some sort is generally used to hold the line temporarily. Prior art type devices will not perform safely under wet or dry conditions and are generally not flexible enough to permit ease of handling. In addition the prior art devices cannot maintain strength and dielectric properties under adverse whether conditions in order to prevent shorting of the lineman's insulation from ground as conventional lanyards can do. It is desirable for a safety line to be able to maintain a dielectric strength of 45KV per foot after prolonged submersion in at least two-and-a-half feet of water while still being able to maintain a minimum breaking strength of 3,500 pounds.
Many prior art type synthetic ropes, slings and lanyards presently on the market are good dielectrically when dry, free of dirt and other work environment contaminents. However, when wet due to rain or condensation, they are completely shorted by moisture which is absorbed into and between strands of the lineman's composition.
When working with high-voltage components, the majority of utility companies use aerial lift bucket trucks with insulating liners inside the buckets. This liner is used as a secondary or back-up insulation to the lineman's primary insulation which is rubber gloves. The liners are quite costly and a majority of utilities using these liners dielectrically test them periodically as required by various regulations.
The federal government OSHA regulations do require lanyards or safety lines from the boom of the truck to the lineman's safety belt but these safety regulations do not specify that these lanyards must have dielectric strength.
When a lineman is performing line work out of a bucket truck, his insulation from ground is (1) the rubber gloves, (2) the bucket liner, and (3) the fiberglass boom. Since the federal OSHA regulations require lanyards attached from the man to the boom, the lanyard must maintain its dielectric integrity or the secondary insulation provided by the liner is shorted out and the lanyard will connect the man electrically to the boom resulting in bypassing the first and second insulation components, leaving the third (fiberglass boom) as the only protection.
Other considerations with respect to the need for an electrically sound lanyard is the possibility of contact to grounded objects such as trees, cross-arms, pole, and pole ground wire when working live lines. In addition accidental contact of lanyards can be made to opposite phases from which the man working again resulting in serious injury and/or death.
By referring to FIGS. 1-3 of the drawings there is shown illustrations of the beforementioned dangers. For example in FIG. 1 there is shown the condition of an electrical worker working in an aerial bucket in the rain with the aerial bucket 10 being attached to an insulated aerial boom 12. The worker 14 is shown working on a high-voltage wire 16 and has connected to his waist a safety line 18 which is also connected to the insulated aerial boom 12. In the example shown the safety line 18 may accidentally come in contact with a tree 20 which would electrically ground the safety line causing serious injury to the worker 14.
In FIG. 2 is shown another condition wherein the worker 14 is standing on an insulation hot board 22 which is mounted on a power pole 24. The worker 14 is working on a high-voltage wire 26 while he has his safety line 18 attached to the insulated hot board 22 as shown in the drawing. In this situation the worker 14 may be accidentally grounded as his safety line 18 contacts a second high-voltage wire 28 of opposite polarity resulting in injury and/or death.
In FIG. 3 of the drawing there is shown a situation wherein an energitized high-voltage wire 30 is connected to a grip 32 which is used to pull up and hold the high-voltage wire 30 as desired. The grip 32 is connected to an insulated safety line 18 which is in turn connected to a cable block 34 and ultimately to the pole 36 through the X arm 38. The safety of the application is dependent upon the insulating qualities of the insulated safety line 18 of the prior art type.
Attempts to find completely waterproof insulating safety lines available on the market were unsuccessful. Various prior art lines were claimed to be dielectrically sound under wet conditions, but when wetted and submitted to high voltages, these lines failed electrical wetting tests. Various synthetic layer coatings such as rubber and silicone coating were applied to these prior art safety lines; however, none of these coatings stopped water penetration in and between the fibers of the safety line and ultimately failed dielectric tests when wet.
Attempts were also made to coat a poly-dacron line with an air cured filler and covering that line with a soft poly-vinyl sleeve. This attempt failed because the filler would not cure unless exposed to the atmosphere and also because the poly-dacron fibers were too fine to prevent capillary action of water when submerged.
A prior art search of pertinent patents was conducted in the U.S. Patent Office and the following United States and foreign patents were uncovered as a result of that search:
______________________________________ Patent Number Country ______________________________________ 1,167,125 United States 2,683,185 United States 2,750,152 United States 2,997,529 United States 1,282,731 France 1,395,704 France 775,112 Great Britain 775,773 Great Britain ______________________________________
None of the above patents cited were directed to the applicant's non-conductive safety line but appeared to be directed to suspension lines, lineman's poles, are the like. In addition none of the references disclosed the concept of utilizing a rope with a covering sleeve in which a dielectric ompound was injected into spaces between the sleeve and the rope which is taught by the applicant's invention.